This invention relates to a system for detecting a multi-sheet feed from multi-tray sheet feeders and from an intermediate or buffer sheet stacker or tray which receives sheets from the multi-tray sheet feeders.
It is common to employ a multi-tray sheet feeder with laser printers. The sheets are fed from the multi-tray sheet feeder to an intermediate or buffer sheet tray and then fed into the printer from the intermediate or buffer sheet tray. It is important that only one sheet at a time be fed from the multi-tray sheet feeder and from the intermediate tray and if more than one sheet is fed from the multi-tray sheet feeder or from the intermediate tray, that it be detected immediately and the system be shut down to correct the situation or the offending sheets can be sent to a purge tray at the printer without shutting down the system. The sheets in one tray of the multi-tray sheet feeder may be of a thickness which is different than the thickness of the sheets in another tray of the multi-tray sheet feeder and therefore, the intermediate tray can contain sheets of different thicknesses. Therefore, there must be a way of detecting a double sheet feed of sheets of the same thickness from each of the multi-tray sheet feeders and a way of detecting a double sheet feed from the intermediate tray which can contain sheets of various thicknesses.